Prime Minister Malcolm Turnbull's Valentine's Day message to his wife has upset marriage equality supporters, with many slamming his Facebook post.

Mr Turnbull described the happiness and joy of his marriage in the post dedicated to his wife Lucy and published this morning.

"When I first asked Lucy to marry me she said, "Let's wait until we grow up." Well we didn't wait long and now it is almost impossible to imagine, let alone remember, what it was like not to be together, so much so that I have a much clearer sense of "Lucy and me" than I do of "me"," he wrote.

Supporters of marriage equality have since commented on the post, highlighting the seeming unfairness of equivalent recognition for same-sex couples.

"Well because of you and your party I will never know what it will be like to marry my parter [sic] of nearly 10 years. So happy for you both," Tomas Allan Leaumont wrote.

"When I first asked my partner to marry me, he said let's wait till our government lets us...and now, four years later, we have to wait until 51 per cent of the country lets us (and then the government an still reject it)...you and Lucy are beautiful together, an inspiring couple...just wish your leadership was more inspiring on marriage…" Douglas McFarland wrote.

Other commenters congratulated Mr Turnbull on his marriage.

The post has been liked more than 29,000 times and shared more than 360 times.

Mr Turnbull married his wife in 1980 and they have two adult children.

Malcolm Turnbull shared an image of himself and his wife in the Facebook post. (Facebook)